Abstract: Bifidobacterium 22-5 from centenarians’ faeces produces an exopolysaccharide containing Xyl, Gal, Glu, Ara, Rha and Fuc. Infrared spectroscopy revealed that it contained pyranose, possessing the carboxyl group and a certain amount of carbonoxlate, and even the cycle ether. In addition, based on GC-MS, methylation analysis, NaIO4 oxidation and Smith degradation, the primary structure was elucidated. EPS was identified as a polymer containing 4-linked D- galactose. D- glucose partially took the form of the 2,3,4,6 connection, and 1-4 or 1-4,6 and 1-2 or 1-2,6 linkages, having neither 1-6 nor 1-linkages. Besides, D- glucoses and D-galactose may be as highly branched parts of the chain. It was also showed that the EPS may have the configure of helix in the Congo red test.

Key words: bifidobacterium, exopolysaccharide, polysaccharide, structure